The present invention relates generally to the field of manhole and gate valve construction and specifically to structures that effectively prevent or substantially limit infiltration of liquid, water, into the manhole or gate valve area. In particular, the structures of the present invention relate to sealing against the surfaces of a manhole or gate valve through which water infiltration between the manhole casting or portions thereof or portions of the gate valve structure may occur. Additionally, the present invention relates to structures which prevent water seepage through the supporting structure of a manhole or gate valve structure and problems related to ground settling or filling in around the gate valve structure.
In conventional manhole assembly or gate valve assembly a manhole casting, which is the uppermost portion of the assembly and serves as the seat of the manhole cover, rests or is fastened to a supporting structure. The supporting structure may be a manhole cone or there may be one or more adjusting rings between the cone and casting. Sometimes the combination of the cone and castings are referred to as the cone. This is just a shorthand for referring to the supporting structure. When the adjusting rings are used the portion of the structure intermediate the casting and the cone is typically called a manhole chimney. The interface between the casting and cone or adjusting ring on which it rests consists generally of two opposing flat surfaces.
Manhole chimneys have normally been constructed with pre-cast rings or with brick or block and have been used on manhole cones constructed from pre-cast sections or of brick or block or cast in place of concrete. Existing manhole assemblies may also have had castings shimed with wood or bricks and mortar placed in the gaps between the shims.
Unfortunately, conventional manhole assemblies can allow for infiltration of surface water into the manhole at the interfaces or locations where the casting and the cone meet or between the casting and the adjusting rings, or between the adjusting rings.
Consequently, as the manhole assembly ages the problem of water infiltration becomes more severe due to the deterioration of the supporting structure.
This deterioration is due, in part, to the movement and settling of the earth and also due to the freeze/thaw cycle common to much of the United States during the winter and spring. This causes a breakdown in the interfaces in the manhole assembly. The expansion/contraction causes cracking and gaps form. Surface water easily infiltrates between the gaps resulting from the deteriorated interfaces.
Additionally, the vibration of passing traffic striking the manhole can also lead to deterioration. Manhole assemblies are commonly located beneath the surface of a road, with the manhole cover and top portion of the casting being flush with the road surface. The weight of vehicles passing over the assembly commonly causes interfaces to deteriorate and also creates cracks in the road surface surrounding the manhole assembly. This can allow surface water to run through these cracks and infiltrate the deteriorated structure.
These factors can also cause a vertical or horizontal displacement of the casting relative to the supporting structure which further increases the probability of water infiltration. Water or liquid infiltration into the sewer collection system represents a major problem in sewage treatment. The capacity of a sewage treatment system in large part is a measure of the volume of the effluent it can treat. Water infiltration during rain storms or during periods of extended rainfall activity adds to the total volume of effluent treated. This increased volume flow may overload new or old sewage treatment systems. In most cases, the excess volume of the effluent overload is dumped untreated in rivers and lakes.
This is not acceptable. It is believe that water infiltration through manhole assemblies is one of the primary contributions to the overloading of sewage treatment systems.
Another problem which results from surface water infiltration of manhole assemblies is the broad dissemination of contaminated surface water, especially when the contaminate is a petrochemical or dangerous pollutant. Contaminated surface water which infiltrates the sewage system through a manhole will be distributed to other cites by the sewage lines or water runoff lines to which the manhole assemblies are connected. Thus, a contaminate that should be contained and disposed of safely away from population centers is instead widely dispersed in an uncontrolled fashion.
Accordingly, it is desired to prevent not only liquid infiltration into a sewer system but the infiltration of liquids which have been properly been deposited into the sewer system from leaving the sewer system or leaching into the surrounding ground. Consequently, there is a continuing need in the field of the present invention for an apparatus to seal the assembly against surface water infiltration. There is also a need for a seal to be effective against infiltration occurring in the area between the casting and the supporting structure and through the supporting structure. There is also a need for a seal that can accommodate vertical and horizontal displacement of the casting relative to the supporting structure during prolonged use. There is also a need for the seal to be economically manufactured and simply constructed so that it may easily be applied in the field. There is also a need for a seal that does not interfere with normal use of the manhole.
Additionally, there is a need for seals for use in conjunction with gate valve adapters. Gate valves are used to control the flow of water and other fluids through underground piping. These valves are buried in the ground. In order to operate the valves, a key is used to turn the operating nut of the valve. The valve is mounted on the end of a long rod in order to reach the operating nut on the valve. Access to the operating nut is generally provided through a key box having a bonnet that is placed over the gate valve to prevent the operating nut from being buried in the ground. The bonnet is generally supported on wood blocks located on each side of the gate valve. As a result of settling of the ground or deterioration of the block the key box bonnet often shifts with respect to the gate valve allowing the ground to enter the bonnet and make it difficult to operate the operating nut. Accordingly, the key box may not operate or may not allow proper setting of the gate valve. This creates problems associated with backfilling, settling, shifting, or an improper setting of the key box over the valve. The present seal structure of the present invention disclosed herein is design to prevent liquid infiltration and inadvertent settling or shifting of a gate valve box. Accordingly the present invention eliminates the usual problems associated with backfilling, settling, shifting or improper setting of the key box over the valve and ensures a perfect setting of the key box on the gate valve.